عنوان مقاله [English]
By 2070, approximately 140 million of the world’s population will have resided in coastal areas and in the vicinity of rivers and thus economist forecast that around 30000 million euro of assets could be dependent on flood protection. A large part of these flood protection systems are old and need replacement and / or adjusted to match safety standards. It needs a significant investment in addition to population pressures increase in coastal areas. Eembankment structures are built of erodible (earthen) and/or non-erodible (Concrete) material by humans or formed naturally. These are used as flood protection system and water storage for drinking and irrigation, energy production, and recreation purposes. Due to various reasons, such as overtopping, seepage, internal erosion and piping, and slope instability earthen embankments may fail. However, more than 34% dam, 35% of earth dams throughout the world and 30% dam failure in USA during the last 80 years due to overtopping. More than 60% of human casualties resulted from the failure of dams due to the failure of the three large dams (Vajont dam (Italy), John Storm dam (USA) and Mucho dam (India) due to overtopping flow. Heavy rainfall and consequent dramatic increase in water level, or wave attack caused by hurricane and earthquake are regarded the primary factors in creating overtopping flow. Inadequate free height, limited capacity of weirs and inaccurate prediction of the most likely flood are among the most well-known human factors. Laboratory experiments are carried on overtopping of embankments consisting of silty sand constructed with different levels of compaction. Digital image processing was employed to investigate the surface variation in embankment due to overtopping erosion with time. The results show that a direct relationship exists between relative density of soil and erosion duration. It is also an inverse relationship between density and rate of erosion. In other hand, relative compaction has a key role in headcut erosion and is clearly evident that in the rate of erosion.